Expandable cardiac harness for treating congestive heart failure

ABSTRACT

A cardiac harness for treating congestive heart failure is disclosed. The harness applies elastic, compressive reinforcement on the left ventricle to reduce deleterious wall tension and to resist shape change of the ventricle during the mechanical cardiac cycle. Rather than imposing a dimension beyond which the heart cannot expand, the harness provides no hard limit over the range of diastolic expansion of the ventricle. Instead, the harness follows the contour of the heart throughout diastole and continuously exerts gentle resistance to stretch. Also disclosed is a method of delivering the cardiac harness to the heart minimally invasively.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to mechanical systems for treatingcongestive heart failure. Specifically, the invention relates to devicesthat interface mechanically with a patient's failing heart in order toimprove its pumping function.

[0003] 2. Description of the Related Art

[0004] Congestive heart failure (“CHF”) is characterized by the failureof the heart to pump blood at sufficient flow rates to meet themetabolic demand of tissues, especially the demand for oxygen.Historically, congestive heart failure has been managed with a varietyof drugs. There is also a considerable history of the use of devices toimprove cardiac output. For example, physicians have employed manydesigns for powered left-ventricular assist pumps. Multi-chamber pacinghas been employed to optimally synchronize the beating of the heartchambers to improve cardiac output. Various skeletal muscles have beeninvestigated as potential autologous power sources for ventricularassist. Among these, dynamic cardiomyoplasty using the latissimus dorsimuscle has attracted the most interest. It has been suggested that thebeneficial effects of this procedure stem from both an active, dynamic,systolic assistance and a passive, adynamic girdling of the heart thatlimits diastolic stretch of the ventricle.

[0005] To exploit these beneficial clinical features, researchers andcardiac surgeons have experimented with prosthetic “girdles” around theheart. One such design reported in the literature is a prosthetic “sock”that is wrapped around the heart. Others have proposed the applicationof an intraventricular splint to reduce the volume of the leftventricle. Several design shortcomings are apparent with each.

[0006] The intraventricular splint, for example, extends through theleft ventricular wall. Consequently, some components of the splintcontact the patient's blood. This creates the potential forthrombogenesis, or the generation of blood clots. In addition, splintplacement requires perforation of the ventricular wall, which may leadto leakage problems such as hemorrhage or hematoma formation.Furthermore, because one end of the splint extends to the epicardialsurface of the left ventricle, options for the orientation of the splintare limited.

[0007] Pulling opposite walls of the ventricle closer together mayreduce average wall stress via LaPlace's law, by reduction inventricular diameter. However, this may create an irregular ventricularwall contour. This creates stress concentrations in the regions of theventricle that are between the localized compression points.Consequently, this may lead to aneurysm formation, fibrosis, andimpairment of the contractility and compliance of the ventricle. Also,the resulting irregular contour of the endocardial surface of the leftventricle may lead to localized hemostasis or turbulence, which may inturn lead to thrombus formation and possible thromboembolism.

[0008] Coronary artery disease causes approximately 70% of congestiveheart failure. Acute myocardial infarction (“AMI”) due to obstruction ofa coronary artery is a common initiating event that can lead ultimatelyto heart failure. This process by which this occurs is referred to asremodeling and is described in the text Heart Disease, 5th ed., E.Braunwald, Ch. 37 (1997). Remodeling after a myocardial infarctioninvolves two distinct types of physical changes to the size, shape andthickness of the left ventricle. The first, known as infarct expansion,involves a localized thinning and stretching of the myocardium in theinfarct zone. This myocardium can go through progressive phases offunctional impairment, depending on the severity of the infarction.These phases reflect the underlying myocardial wall motion abnormalityand include an initial dyssynchrony, followed by hypokinesis, akinesis,and finally, in cases that result in left ventricular aneurysm,dyskinesis. This dyskinesis has been described as “paradoxical” motionbecause the infarct zone bulges outward during systole while the rest ofthe left ventricle contracts inward. Consequently, end-systolic volumein dyskinetic hearts increases relative to nondyskinetic hearts.

[0009] The second physical characteristic of a remodeling left ventricleis the attempted compensation of noninfarcted region of myocardium forthe infarcted region by becoming hyperkinetic and expanding acutely,causing the left ventricle to assume a more spherical shape. This helpsto preserve stroke volume after an infarction. These changes increasewall stress in the myocardium of the left ventricle. It is thought thatwall tension is one of the most important parameters that stimulate leftventricular remodeling (Pfeffer et al. 1990). In response to increasedwall tension or stress, further ventricular dilatation ensues. Thus, avicious cycle can result, in which dilatation leads to furtherdilatation and greater functional impairment. On a cellular level,unfavorable adaptations occur as well. This further compounds thefunctional deterioration.

[0010] Some have proposed that an elastic wrap around the heart mightattenuate the remodeling process that is actively underway in failinghearts, prompting treatment with latissimus dorsi cardiomyoplasty. Basedon experimental work to date, passive latissimus dorsi muscles appear tobe best suited for this application. Oh et al. (1997) publishedexperimental work in which they found a relatively inelastic prostheticfabric wrap to be inferior to adynamic latissimus dorsi in bringingabout reverse remodeling in an experimental model of heart failure. Thiswas attributed to the greater elasticity of the muscle wrap.

[0011] It is thought that application of a device to provide compressivereinforcement similar to that of adynamic cardiomyoplasty might betherapeutic in treating dilated, failing hearts. Because heart failureis only the clinical end-stage of a continuous remodeling process, sucha device might be able to attenuate or stop remodeling after amyocardial infarction far before the onset of heart failure. Such adevice would have different functional requirements from a device thatis used solely to treat established heart failure.

[0012] One requirement is to provide a slight elastic compression to theepicardial surface of the left ventricular wall. The device should allowexpansion and contraction of the heart, but continue to apply gentleelastic compression to the left ventricle. This would reducecircumferential and longitudinal wall tension, thereby improvingefficiency, lowering energy expenditure, reducing neurohormonalactivation, encouraging favorable cellular changes, and stabilizing thedimensions of the heart. This mechanical action is often referred to as“myocardial sparing.” The device should effect myocardial sparingwithout limiting the motion or the dimensions of the heart. Nor shouldit actively change the shape of the heart by pulling it or squeezing it.In fact, imposing a rigid barrier to limit distension or to squeeze theheart can be potentially dangerous. Shabetai in The Role of thePericardium in the Pathophysiology of Heart Failure notes that thepericardium exerts 3-4 mm Hg of pressure against the heart. Cardiacfunction can be adversely affected with just a slight increase inpericardial constraint. For example, cardiac tamponade begins to be seenwith pericardial pressures as low as 5-10 mm Hg.

[0013] A second requirement of such a device is to provide reinforcementthat prevents the further shape change of the left ventricle withoutacutely changing the shape by its application. The device would act toprevent both global dilatation toward a more spherical shape and localinfarct expansion after a myocardial infarction. In fact, if the localinfarct expansion can be minimized with such a device, the compensatoryglobal dilatation and increase in sphericity may be prevented. What isneeded is a mild compressive support that conforms to the epicardialcontour. As the left ventricle or portions of the left ventricle distendoutward, they would be met with greater pressure from the device. Thepresence of the device would likely cause the left ventricle toreverse-remodel and its dimensions to stabilize and even shrink. As thisoccurs, the device would be able to shrink with the left ventricle likea latissimus dorsi muscle. The device would supply less pressure as thediameter decreases. Conversely, the device would supply graduallyincreasing pressure as the diameter or local distention increases. Thisideal was expressed by Oh et al. in their description of the benefits ofa passive latissimus dorsi muscle wrap.

[0014] The ability of the device to conform to the heart as it shrinksor expands is of great importance. A device would need to possessconsiderable elasticity in order to do so. The left ventricle in adilated, failing heart does not distend significantly because smalldiameter changes are sufficient to achieve the necessary stroke volume.In contrast, a normal heart has a much smaller left ventriculardiameter. For example, Li (1997) noted that to achieve a 70-cc strokevolume, a normal left ventricle of 2.8 cm radius contracts down to 1.7cm, a 40% decrease. However, a dilated ventricle of 4.5-cm radiusachieves the same stroke volume by contracting to 4.2 cm, only a 7%decrease. Thus, in order to achieve the same stroke volume as a dilatedheart, the normal heart's ventricular diameter must change by a greateramount. Consequently, a device with sufficient elasticity for treatingdilated hearts in established heart failure may not be able to treat aheart of normal dimensions that has suffered a myocardial infarction.

[0015] The ability of a harness to conform to the heart is alsotheoretically important in preventing dilated heart failure after acutemyocardial infarctions because it may be important to providereinforcement during systole, especially early systole. Prostheticfabrics impose a relatively inelastic barrier that acts only at theend-limits of diastole. In addition to providing more myocardial sparingover a greater portion of the cardiac cycle, a device that remains incompressive contact with the heart into systole would counteract the“paradoxical bulging” of the infarct region that occurs in dyskinetic,aneurysmal hearts during systole. This may attenuate infarct expansionand therefore limit the extent of remodeling that further ensues.

[0016] Another problem with the inelastic nature of fabric wraps, orknits, is that normal, healthy changes in the dimensions of the heartare not accommodated. In addition to chronic pathologic changes inventricular diameter that can occur, such as those that accompanyremodeling, normal physiological changes also occur. For example, inorder to keep up with increased metabolic demands from physical exertionor exercise, the heart may dilate acutely. A wrap must be able toaccommodate these increases without imposing excessive pressures.

[0017] An important problem with the use of fabrics, such as knits andweaves, as well as with other materials previously used for thisapplication, is their dimensional coupling between orthogonaldirections. When stretched in one direction, there is considerableforeshortening in the perpendicular direction. Typically, the greaterthe elasticity present, the greater the foreshortening that is seen inthe perpendicular direction. When used in a wrap around the heart, sucha material can lead to serious problems. The greatest distension andwall stress is oriented in the circumferential direction around the leftventricle. Therefore it is logical to align the more compliant directionof the fabric to be parallel to it. As the left ventricle fills and thediameter increases, the fabric stretches in the circumferentialdirection. This causes shortening in the longitudinal direction, whichis perpendicular to the direction of stretch. When used in a cardiacwrap, this results in increased sphericity of the ventricle duringdiastole, relative to the unwrapped heart. Sphericity is defined as theratio of the diameter to the length of the heart or ventricle. Increasedsphericity of the left ventricle is associated with decreased survivaland an increased incidence of mitral regurgitation. Kono (1992) andDouglas (1989) documented this in published studies. There is a need fora structure that does not foreshorten and increase sphericity as itprovides elastic, compressive reinforcement to the heart, especially theleft ventricle.

[0018] Since the mid 1980's a promising procedure has been evaluatedclinically. The procedure, dynamic cardiomyoplasty, involves surgicallydissecting the patient's latissimus dorsi muscle, introducing it intothe thoracic cavity, and then wrapping and attaching the muscle to theheart. An implantable electrical stimulator is connected to the musclein order to stimulate and pace it in synchrony with the heart. Thiscauses the muscle to contract and also transforms the muscle, making itmore fatigue-resistant. The original premise behind dynamiccardiomyoplasty was that these muscle contractions, by virtue of thegeometry of the wrap, would squeeze the heart, and thus provide systolicassistance. If successful, an essentially patient-powered, relativelyinexpensive, non-blood-contacting, easily placed ventricular-assistdevice could be employed.

[0019] The first reported clinical case of dynamic cardiomyoplasty usinga latissimus dorsi wrap was published in 1985. Since then, over 1,000patients have been treated with this experimental procedure. Numerouspublished studies have shown that the procedure produces significantimprovement in clinical status, as graded by the New York HeartAssociation (“NYHA”) classification scale, a slight but significanthemodynamic or systolic function improvement, and a reduction in thenumber of patient hospital visits after the procedure. However, animprovement in survival has yet to be consistently demonstrated.Furthermore, perhaps due to their frail condition, NYHA class IVpatients have not fared well with the procedure. This has limited itsuse to NYHA class III patients. It appears that the skeletal musclewrap, probably because of its deterioration over time, does not providesustained squeezing of the heart over time. Yet, the clinical benefitsof the procedure appear to persist. This paradox has led to considerableresearch into the underlying mechanisms of dynamic latissimus dorsicardiomyoplasty.

[0020] This research has resulted in several independently additivehypothetical mechanisms to explain the benefits of dynamiccardiomyoplasty. The original concept of systolic squeezing of theheart, in particular the left ventricle, was shown in experimental workto provide hemodynamic benefit. But there additionally appears to be aconsiderable benefit derived from the presence of the passive,unstimulated latissimus dorsi wrap alone. Drs. Chiu (1992), Carpentier(1993), and others hypothesized that the presence of the latissimusdorsi wrap provides a beneficial passive function beyond the benefits ofsystolic-squeezing augmentation. It was speculated that the muscle wrapacts as a girdle around the heart. The girdle is thought to impose aphysical limit on the heart to prevent it from dilating beyond itsboundaries. This is commonly referred to as the “girdling” effect. Aseparate and equally powerful hypothesis was that the muscle wrap helpsthe native myocardium bear some of the load, in essence reducingmyocardial tension or wall stress, via Laplace's law, by creating athicker wall. This has been referred to as the “myocardial sparing”effect by virtue of the reduction in wall stress and concomitantreduction in oxygen consumption. The benefits of these two passivemechanisms are thought to be additive with the systolic squeezingbenefits of cardiomyoplasty. Published experimental work by Nakajima etal. (1994), Chen et al. (1995), Kawaguchi et al. (1992 & 1994), Kass etal. (1995), Capouya et al. (1993), Chekanov (1994) and others providesupport to the validity of the hypothetical mechanisms.

[0021] The concept of using a permanently implantable passive,non-contracting wrap around the heart to prevent its furtherdeterioration is not new. Suggestions have been published in theliterature. Kass et al. (1995) questioned whether an “artificial elasticsock” could be used in lieu of skeletal muscle. They speculated that indynamic cardiomyoplasty, the latissimus dorsi wrap provides some of itsbenefit by acting as an elastic constraint around the epicardialsurface. They further suggest that the passive skeletal muscle wrapstiffens gradually with stretch, unlike pericardium, which is highlycompliant at low levels of stretch but becomes very stiff when expandedbeyond resting dimensions. Throughout the article, the importance ofgradually increasing stiffness over the entire range of cardiacoperating dimensions is emphasized. Despite the conceptual discussion,however, there is no mention of how a cardiac wrap that is both elasticover the entire range of cardiac dimensions and gradually stiffens withstretch can be designed or built.

[0022] Vaynblat et al. (1997) report on the experimental use of anexpanded polytetrafluoroethylene (“ePTFE”) prosthetic wrap in animals.They constructed the wrap from sheets of ePTFE material that were sizedto the heart and sutured to finish the wrap. ePTFE has very limitedelasticity and stretch. The ePTFE sheet wraps were shown to reduceventricular dilatation in a failing-heart model, but they did notimprove cardiac function.

[0023] Oh et al. (1998) report on a similar study using a Marlexpolypropylene mesh sheet material. In this study they compared thebenefits of unpaced, adynamic latissimus dorsi muscle wraps with thoseconstructed of Marlex sheet material. It was found that the latissimusdorsi wrap attenuated dilatation of left ventricle in a failing heartmodel to a greater extent than the Marlex wrap. The superiority of thelatissimus dorsi wrap was attributed largely to its “elasticstretchability” and the resulting dynamic constraint that it provided.This “yield-and-support” characteristic could not be attained usingprosthetic membranes, such as Marlex and ePTFE. In addition, thefibrotic reactions that are likely to be induced by the prostheticmembranes have a further adverse effect on compliance. In furthersupport of the contention made by Kass, Oh et al. state that pericardium“shows virtually no restraining effect on chronic cardiac dilatation.”Despite this, the authors mention that latissimus dorsi cardiomyoplasty,whether dynamic or adynamic, is a very invasive and complex surgicalprocedure. The exclusion of NYHA Class IV patients from the dynamiccardiomyoplasty clinical trials was partially attributed to this. Oh etal. suggest that cardiac binding with a prosthetic membrane may still beof value, even with shortcomings, because it lends itself to minimallyinvasive surgical techniques.

[0024] None of these prosthetic cardiac wraps operates elastically inthis manner over the entire range of cardiac dimensions. Thus, only an“end-girdling” effect is provided. The myocardial sparing effect is onlypresent for a brief moment at the end of diastole. In addition, becausethese inelastic wraps counteract dilatation at the limits of diastole,they prevent the heart from expanding beyond that dimensional limit toaccommodate increased physiological demand, such as during exercise. Inaddition, even if the wraps could bring about desirablereverse-remodeling and shrinkage of the heart, a wrap, due to its fixedcircumference, may not be able to shrink evenly with a heart whosecircumference is decreasing. In fact, the prosthetic wraps may interactwith the heart like a fiber-reinforced composite material and even fixor “cement” the circumference and diameter of the heart, such that it isunable to shrink.

[0025] Because the three underlying mechanical mechanisms of dynamiccardiomyoplasty discussed above are considered to be independentlyadditive, it is thought that the addition of active systolic assistanceto the heart would be more beneficial than a passive wrap alone. In apublished experiment by Mott et al. (1998), dynamically paced latissimusdorsi was compared with unpaced, adynamic latissimus dorsi in anexperimental heart failure model. It was found that the dynamic, pacedwrap was capable of reversing remodeling to a much greater extent thanan unpaced latissimus dorsi wrap. Mott et al. also speculate thatperhaps the dynamic and adynamic functions of latissimus dorsi wrapsprovide complimentary benefit to failing hearts. The adynamic wrapprovides reinforcement only during diastole, while the dynamic wrapprovides reinforcement during systole.

[0026] Additional support for this idea can be found in publishedanecdotal reports of documented hemodynamic deterioration in patients inwhom cardiomyostimulators malfunctioned and ceased to providestimulation to the latissimus dorsi wrap. This further suggests that thesystolic assistance mechanism may provide increased benefit compared toa passive girdle alone.

[0027] Despite the prevailing sentiment that stimulated latissimus dorsiwraps should be more beneficial than non-stimulated wraps, the manner inwhich dynamic cardiomyoplasty has been executed clinically has limitedits clinical success and therefore its acceptance. The underlyingmechanisms of dynamic cardiomyoplasty have been the focus of substantialinvestigation.

[0028] Preservation of the latissimus dorsi as a power source has alsobeen an issue. Because of muscle atrophy and fibrosis, the amount ofsqueezing power that is available has not been sustainable. Ischemia,especially to the distal portion of the muscle whose blood supply wasinterrupted by surgical dissection, has been considered to be a majorcause. In addition, some have speculated that damage to thethoracodorsal nerve during the procedure and as a result of therelocation of the muscle is a cause of loss of contractility of themuscle. Another possible problem is the unnatural configuration in whichthe muscle is forced to operate. The preloads and afterloads againstwhich the muscle works are clearly altered from those of in situlatissimus dorsi.

[0029] The complexity and invasiveness of the dynamic cardiomyoplastysurgical procedure has been implicated as well. Even if the muscle wereto remain viable in the long term, there are some physical limitationsto its ability to provide the systolic assistance that was once the hopeof dynamic cardiomyoplasty. Cho et al. (1994) published a study in whichthree-dimensional magnetic resonance imaging (3-D MRI) reconstructionwas used to analyze experimental dynamic cardiomyoplasty. The authorsfound that muscle wrap stimulation brought about considerabletranslation of the heart in the plane of the short axis of the leftventricle and rotation about the long axis. Little short-axis or radialsqueeze was seen. However, long-axis compression was observed. Thislong-axis compression was confirmed in a similar study published byPusca et al. (1998). This suggests that the muscle power provided by thelatissimus dorsi is not channeled very efficiently into systolicassistance.

[0030] One observation by Hayward is especially noteworthy. The authorsuggested that the contractile properties of the distal portion of thelatissimus dorsi muscle in dynamic cardiomyoplasty degenerates the most.This is attributed to ischemia and the use of the muscle in aninefficient configuration. Yet, this is the portion of the muscle thatis in contact with and expected to squeeze the heart. The proximalportion of the muscle, which is better perfused and oriented in a morelinear, efficient, and natural configuration, does not contact with theheart. As such, stimulation of the muscle is likely to result in morecontraction of the proximal portion of the muscle, the portion that doesnot squeeze the heart. Contraction of this portion of the muscle causesthe heart to translate and rotate as observed experimentally by Cho.Because the heart is attached to the great vessels at its superior end,it would be expected to behave as if it were attached to a pivot at thispoint. Thus, any lateral force or moment applied to the heart shouldresult in lateral translation and rotation. However, in thissuperior-pivot hypothesis, there should be less freedom to translatevertically. Therefore, any vertical force applied to the heart wouldlikely cause longitudinal compression rather than translation. Thus, itis not surprising that stimulation of the muscle results in moretranslation, rotation, and lifting of the entire heart.

[0031] Even if the distal portion of the latissimus dorsi muscle remainsviable, there may be a physical limit to how much systolic hemodynamicbenefit it can provide. The overall volume of the left ventricle is moresensitive to changes in its short-axis dimension, i.e., its diameter,than its long-axis dimension, i.e., its length. For example, the volumeof a cylinder is proportional to its length and to the square of itsdiameter. It would thus be expected that the greatest change in volumecould be brought about by a change in the diameter of the ventricle.Skeletal muscle such as the latissimus dorsi is capable of shorteningless than 15% over its length. Assuming that the muscle is adhered tothe epicardium, the circumference of the heart would only be capable ofshortening 15%. For approximation purposes, the left ventricle can betreated as a cylinder. If the circumference of a cylinder of 5-cmdiameter shortens by 15%, then the volume of the cylinder changes byapproximately 28%. It is interesting to note that this number isconsistent with the maximum ejection fractions that have been achievedclinically and experimentally. A device that does not have thelimitation of 15% stretch or shortening might be able to overcome thisejection-fraction limitation and provide more hemodynamic improvement,particularly in cardiac output. Poor increases in ejection fraction andcardiac output have been cited as a shortcoming of the dynamiccardiomyoplasty procedure.

[0032] Another limitation of dynamic cardiomyoplasty is the potentialmismatch between the orientation of the direction of shortening of thelatissimus dorsi muscle fibers and that of the epicardium. The principaldirection of shortening corresponds to the direction of muscle fiberorientation of each. Although the myocardial muscle fiber orientationvaries in the left ventricle, the principal direction of shortening hasbeen reported to follow the epicardial muscle fiber orientation, whichfollows a left-handed helical orientation from the apex to the base ofthe chamber. If it is assumed that the latissimus dorsi becomes adheredto the epicardial surface of the heart, then any misalignment betweenthe muscle fibers would result in inefficiency of energy transfer. Eachmuscle shortens and stretches somewhat across the “grain” or fiberdirection of the other. To compound matters, Strumpf et al. (1993)report a significant increase in the stiffness of passive skeletalmuscle in the cross-fiber direction. As a result, the muscle wrap maylimit the extent of myocardial lengthening and shortening, and thuslimit cardiac function.

[0033] An additional source of drag may stem from the inertia added bythe muscle itself. It is estimated that an adult latissimus dorsi muscleweighs roughly 600 grams. This additional weight adds considerableinertia to the heart. This may be responsible for the reportedimpairment of cardiac function immediately following the application ofthe muscle by Corin et al. (1992), Cheng et al. (1992), and as suggestedby Vaynblat et al. (1997).

[0034] Experimentally, passive, unstimulated latissimus dorsicardiomyoplasty wraps appeared to be the best at attenuating remodelingand heart failure. However, in a clinical setting, the surgery requiredto dissect and attach the muscle around the heart is very extensive andtraumatic. Even if such a therapy were proven clinically efficacious,this factor limits its potential acceptance.

[0035] Accordingly, there is still a need in the art for a prostheticelastic wrap that does not foreshorten in the direction perpendicular tothe primary direction of ventricular expansion, and that reduces wallstress by maintaining compressive contact over a significant portion ofthe cardiac cycle. Additionally, there is a need for a device that aidsin preventing, in addition to treating, heart failure after acutemyocardial infarction through attenuation of the remodeling process.

SUMMARY OF THE INVENTION

[0036] Accordingly, it is a principal object and advantage of thepresent invention to overcome some or all of the aforementioneddisadvantages. One aspect of the present invention comprises a cardiacharness for treating or preventing congestive heart failure. The harnesscomprises a plurality of interconnected elastic bending hinges, each ofwhich has a central portion connected on opposite sides to respectivearm portions. The arm portions interact with the central portion inresponse to deflection of the arm portions to create a bending moment inthe hinge to store potential energy.

[0037] In certain embodiments, the cardiac harness comprises bendinghinges that are substantially U-shaped, V-shaped, square-wave-shaped,teardrop-shaped, or keyhole-shaped. Advantageously, at least one of thebending hinges from a first row is connected to another of the bendinghinges from a second row.

[0038] In some preferred embodiments, the bending hinges comprise atleast one strand of Nitinol. The strand(s) can comprise a wire or aribbon.

[0039] In some embodiments, the cardiac harness further comprises apower source that supplies energy to the harness, causing the harness tocontract. That power source may deliver electrical energy to at leastone of the bending hinges, causing at least one of the bending hinges toproduce a bending moment. Alternatively, the power source may delivermechanical energy to the cardiac harness, such as through a cable.

[0040] Advantageously, the power source is programmable viatranscutaneous radio-frequency signals, and can be rechargeable viatranscutaneous electromagnetic coupling, and/or transcutaneous inductivefield coupling.

[0041] In another aspect of the invention, the cardiac harness has aplurality of spring elements, and the harness is adapted to be placedaround at least a cardiac base. The spring elements interact such thatthe harness expands and contracts in a substantially transversedimension of the harness in the region of the cardiac base in responseto the mechanical cardiac cycle, without substantial expansion orcontraction in the longitudinal dimension of the harness in the regionof the cardiac base.

[0042] In another aspect of the invention, the cardiac harness isadapted to be placed around at least a cardiac apex. The spring elementsinteract such that the harness expands and contracts in a substantiallylongitudinal dimension of the harness in the region of the cardiac apexin response to the mechanical cardiac cycle, without substantialexpansion or contraction in the transverse dimension of the harness inthe region of the cardiac apex.

[0043] Another aspect of the invention includes at least one elongatestrip sized to fit around a base of a ventricle, such that the stripextends substantially transverse to the longitudinal axis of the heart.The strip comprises at least one spring element configured to cause thestrip to provide force against the base of the ventricle in asubstantially transverse direction without substantial force in alongitudinal direction. The strip can comprise at least one undulatingstrand.

[0044] In some embodiments, the spring element comprises a centralportion and two arm portions.

[0045] In another aspect, the harness of the disclosed embodiments cantreat or prevent congestive heart failure in a heart having a ventriclethat changes sphericity in response to diastolic filling. The harnesscomprises a plurality of interconnected spring elements, limitingdiastolic distention of the ventricle to a degree of expansion withoutsubstantially altering naturally occurring changes in the sphericity ofthe ventricle through the same degree of expansion caused by diastolicfilling of the heart. Alternatively, the harness can limit diastolicdistention of the ventricle to a degree of expansion while substantiallydecreasing the magnitude of a naturally occurring increase in thesphericity of the ventricle through the same degree of expansion causedby diastolic filling.

[0046] In another aspect of the invention, the harness comprises aseries of interconnected spring elements, each spring element comprisinga central portion and a pair of arm portions extending along respectivepaths that originate at respective sides of the central portion andconverge toward each other along at least a portion of the paths as thepaths extend away from the central portion.

[0047] In a further aspect, the harness comprises first and secondstrands of material, each strand having a plurality of hinges. Each ofthe hinges is formed by a pair of arm portions extending from a centralportion, and each hinge within the plurality of hinges of the firststrand has both arm portions disposed within a hinge of the secondstrand, between the arm portions of the hinge of the second strand. Insome embodiments, at least one of the strands comprises a band.

[0048] Also disclosed is a method of assembling a cardiac harness,comprising providing a plurality of rings, each of the rings having aseries of periodic undulations, each of the rings being unattached toother of the rings, and interconnecting the rings by interleaving theundulations without interrupting continuity of the rings.

[0049] In certain embodiments, the cardiac harness comprisesinterconnected strands of material. The harness also has at least onepad having a marginal edge which is oriented for placement in proximityto at least one coronary artery, so as to reduce compression of theartery by the harness. In further embodiments, the harness comprisesinterconnected strands of material which traverse an exterior surface ofa ventricle of the heart, without traversing a substantial portion ofthe length of at least one of the following coronary arteries: the leftanterior descending artery, the right coronary artery, the leftcircumflex artery, the posterior descending artery, and the obtusemarginal artery. And in some embodiments, the harness comprises asupport member which supports a portion of the strands, the memberhaving side portions disposed on opposite sides of the at least onecoronary artery.

[0050] Also disclosed is an apparatus for delivering a cardiac harnesshaving side portions and an apex portion. The apparatus comprises acatheter body having a distal end portion, configured to retain theharness in a substantially inverted condition with an interior side ofthe harness facing outward away from a ventricle and an exterior sidefacing inward toward the ventricle. The apparatus further comprises anactivation member which is movable distally relative to the catheterbody. The apex portion of the harness is releasably connected to thecatheter body. The activation member drives the side portions of theharness distally and outwardly relative to the apex portion such thatthe harness expands circumferentially. The harness thereby everts to atleast partially surround the ventricle, with the interior side of theharness facing inward toward the ventricle and the exterior side facingaway from the ventricle. In some embodiments, the distal end portioncomprises a suction cup.

[0051] Another aspect of the invention includes a method of delivering acardiac harness onto a heart. The method comprises providing a catheterhaving an inverted harness mounted on a distal end portion of thecatheter, inserting the catheter into a thorax such that an apex portionof the inverted harness is proximate to the apex of a ventricle, andeverting side portions of the harness while the apex portion of theharness remains positioned proximate to an apex of the ventricle.

[0052] Also disclosed is a method of manufacturing a cardiac harness.The method comprises forming an elongate member having undulations froma sheet of material. In a preferred arrangement, forming the elongatemember comprises forming the undulations in a plane substantiallyparallel to the sheet of material. In some embodiments, forming theelongate member comprises cutting the elongate member on a flat surface,and in certain arrangements, the method further comprises annealing thematerial with the undulations oriented at a substantial angle relativeto the plane.

[0053] Further features and advantages of the present invention willbecome apparent to one of skill in the art in view of the DetailedDescription of the Preferred Embodiments which follows, when consideredtogether with the attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054]FIG. 1 is a schematic view of the mammalian heart, with thecardiac harness in place on the heart.

[0055]FIG. 2A-2C illustrate an elastic bending hinge, both in a relaxedposition and under tension.

[0056]FIG. 3 illustrates V-shaped bending hinges.

[0057]FIG. 4 illustrates U-shaped bending hinges.

[0058]FIG. 5 illustrates square-wave-shaped bending hinges.

[0059]FIG. 6 illustrates teardrop-shaped bending hinges.

[0060]FIG. 7 illustrates keyhole-shaped bending hinges.

[0061]FIG. 8A-8E illustrate various types of interconnections betweenstrips or rows of bending hinges.

[0062]FIG. 9A-9C illustrate the principle of decoupling of longitudinalexpansion from transverse expansion of bending hinges.

[0063]FIG. 10A-10B illustrate interlocking of rows of bending hinges.

[0064]FIG. 11A-11B illustrate interweaving of rows of bending hinges.

[0065]FIG. 12 is a schematic illustration of the diameter and lengthdimensions of the cardiac wall.

[0066]FIG. 13 is a graph of the sphericity-versus-volume relationship ofa latex bladder: alone, in conjunction with application of the cardiacharness, and in conjunction with application of a polyester knit sock.

[0067]FIG. 14 is a schematic diagram of the cardiac harness in place onthe heart, with stiffer, thicker hinges covering the left ventricle thanthe right ventricle.

[0068]FIG. 15 is a schematic diagram of the cardiac harness applied onlyto the left ventricle.

[0069]FIG. 16A-16B demonstrate application of two protecting stripsadjacent to a coronary artery, deep to the cardiac harness andsuperficial to the epicardium.

[0070]FIG. 17 is a schematic diagram of a wire frame attached to thecardiac harness and surrounding a coronary artery.

[0071]FIG. 18A-18B are schematic illustrations of a wrap-aroundembodiment of the cardiac harness, with a fastening strip applied to theleading edge of the cardiac harness.

[0072]FIG. 19 is a schematic cross-sectional view of the human thoraxwith a cardiac harness delivery device inserted through an intercostalspace and contacting the heart.

[0073]FIG. 20-20B are cross-sectional elevational side views of acardiac harness delivery device.

[0074]FIG. 21-25 are schematic illustrations of progressive steps in theapplication of the cardiac harness to a heart, utilizing the cardiacharness delivery device.

[0075]FIG. 26A-26D are schematic illustrations of a “flower petal”embodiment of the cardiac delivery device.

[0076]FIG. 27A-27B are schematic illustrations of sharp anchorsextending from the bending hinges of the cardiac harness into themyocardium (heart muscle).

[0077]FIG. 28 is a side view illustration of a bent-body embodiment ofthe cardiac delivery device, proximate to a human heart.

[0078]FIG. 29 is a side view illustration of a straight-body embodimentof the cardiac delivery device, proximate to a human heart.

[0079]FIG. 30-31 show progressive steps in the placement of the cardiacharness on a human heart, utilizing the cardiac delivery device.

[0080]FIG. 32 is a schematic illustration of a cardiac harness appliedto the human heart, with direct application of electrical current to thecardiac harness.

[0081]FIG. 33-34 are schematic illustrations of the cardiac harness inplace on the human heart, together with an actuating device and cablefor application of mechanical force to the cardiac harness.

[0082]FIG. 35a is a schematic top view of a ring of hinges after beingcut from a sheet of material.

[0083]FIG. 35b is a schematic side view of a ring of hinges after beingcut from a sheet of material.

[0084]FIG. 36a is a schematic top view of a ring of hinges after beingtwisted into a beveled configuration.

[0085]FIG. 36b is a schematic side view of a ring of hinges after beingtwisted into a beveled configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0086] The preferred embodiment comprises an apparatus and method fortreating established congestive heart failure (“CHF”), as well as forpreventing its onset after acute myocardial infarction. Althoughreference is frequently made throughout this discussion to CHF caused byacute myocardial infarction, the cardiac harness of the disclosedembodiments can be used to treat CHF caused by forward-pump failure fromany disease, such as idiopathic dilated cardiomyopathy, hypertrophiccardiomyopathy, and viral cardiomyopathy. The harness acts by theapplication of a elastic compressive reinforcement on the left ventricleto reduce deleterious and excessive wall tension and to resist shapechange of the left ventricle during diastole. Use of this harness canattenuate and potentially reverse the remodeling process that occurs inthe left and/or right ventricle following myocardial infarction.

[0087] The harness applies compressive reinforcement around the leftventricle over a significant portion of the cardiac cycle whileminimizing change to the shape of a ventricle and heart. Rather thanimposing a dimension beyond which the heart cannot expand, the preferredembodiment attempts to set no distinct limit to end-diastolic volume.Instead, the apparatus of the preferred embodiment follows the contourof the epicardium and continuously applies a gentle resistance to wallstretch. This avoids the potential to create dangerous restrictive andconstrictive conditions, similar to those seen in restrictivecardiomyopathy, constrictive pericarditis, and cardiac tamponade.

[0088] A great advantage of the harness of the disclosed embodiments isits elasticity. Elasticity refers to the ability of a material or objectto deform and recover its shape when a load is first applied and thenremoved from it. The greater the deformation from which it can recover,the greater is the elasticity of the material or object. Elasticityallows the cardiac harness to conform and apply pressure to the heart asit fills and empties. Elasticity of the harness is achieved by the useof hinges, which can be U-shaped, that bend elastically under load.These hinges can be arrayed or networked in various ways to impart adesired amount of support in a desired orientation, at a desiredlocation. Another advantageous aspect of the cardiac harness is that thehinges are arranged so as to minimize or avoid foreshortening,especially in the longitudinal direction during circumferentialexpansion. This allows the device to reinforce the heart withoutnecessarily altering the heart's sphericity to a great degree.

[0089] In addition to providing passive elastic support of the heart,the device can also provide an interface to the heart that allows theapplication of noncardiac power to assist systolic ventricular function.

[0090] A preferred embodiment comprises an array of connected hingeelements that are configured to be in compressive contact with the leftventricle. In another preferred arrangement, the connected hingeelements are in contact with the right ventricle or with bothventricles. The array of hinge elements provide selective elasticresistance to stretch during diastole and contractile augmentationduring systole. Typically, elastic materials resist deformation with aforce that increases with increasing deformation. This force is storedin the material and is released during the unloading of the material.Because wall stress in the left ventricle is thought to be greatest inthe circumferential direction, the hinges are predominantly aligned toact in this direction, although it may be desirable to have some elasticsupport in the longitudinal direction, or some other direction, as well.

[0091]FIG. 1 illustrates a mammalian heart 2 with the cardiac harness 4applied to it. In this illustration, the cardiac harness surrounds bothventricles, from apex to base. Note that the hinges are relatively smallin this illustrated embodiment, but in other preferred embodiments, thehinges can be larger.

[0092] Each hinge 6 provides unidirectional elasticity, in that it actsin one direction and does not provide much elasticity in the directionperpendicular to that direction. FIGS. 2a-2 c illustrate a preferredembodiment of the elastic hinge. FIG. 2a illustrates how the hinge 6 canbe generally U-shaped with a central portion 8 that has at least oneinner and outer radius of curvature, and two arms 10 extending from thecentral portion 8. The two arms 10 are aligned to be roughlyperpendicular to the primary direction of elasticity. The components ofthe hinge 6 lie flat in a plane parallel to the surface of theepicardium. Thus, when the ventricle dilates in congestive failure, theends of the arms 10 are pulled away from each other, as illustrated inFIG. 2b. This imposes a bending moment on the central portion 8.Mechanically, this creates a state in which there is compression on theoutside of the bend 12 and tension on the inside of the bend 14 in thecentral portion 8 of the hinge 6. These compressive 12 and tensile 14regions are separated by a neutral axis. The stresses can be distributeddifferently by varying the shape of the central portion 8. For example,as illustrated in FIGS. 3-7, the hinges 6 can be V-shaped (FIG. 3),U-shaped (FIG. 4), square-wave-shaped (FIG. 5), teardrop-shaped (FIG.6), or keyhole-shaped (FIG. 7). The deformation and bearing of the loadin the hinge structure 6 is taken up primarily by the bending of thecentral portion 8 and the arms 10. Little load is carried in puretension parallel to the wire direction.

[0093] An advantageous feature is that the hinges 6 are designed suchthat the elastic limit or yield point of their material is not exceededduring use. In other words, the hinges 6 operate in their elastic rangeso that they can recover to their original, stress-free configurationwhen they are unloaded. In addition, an important aspect to the use of aharness 4 comprised of elastic hinges 6 is that the harness 4 is sizedsuch that it remains in elastic, compressive contact with the heart 2.

[0094] Another advantageous characteristic of the elastic bending hinges6 is that they apply increasing resistive force with increasing bending.The more they are stretched, the greater force with which they resist.Overall, a harness 4 constructed of these hinges 6 will behave in asimilar fashion. A goal of cardiac or left-ventricular harnessingaccording to the preferred embodiment is to apply a gentle compressivepressure against the surface of the epicardium of the heart 2. As theleft ventricular wall distends locally or globally, it will be met withincreasing pressure by the hinges 6, locally or globally. Increasedpressure exerted by the harness 4 lowers wall stress within the leftventricle and thus may prevent further infarct expansion, globaldilatation, and remodeling. The cardiac harness 4 according to thepreferred embodiment mechanically resists size and shape changes thattake place in the heart 2 after an acute myocardial infarction. Inaddition, the harness 4 may be capable of reversing the remodelingprocess that occurs post-infarction. If reverse remodeling occurs, andthe left ventricular shape and size consequently decrease back towardnormal, then resistive pressure from the harness 4 will commensuratelydecrease, as well.

[0095] One of the most effective means of limiting infarct expansion andpreventing the onset of the remodeling process after an acute myocardialinfarction is revascularization of infarcted and jeopardized myocardium.Most often this is achieved by coronary artery bypass grafting. Theapplication of a cardiac harness according to the preferred embodimentduring bypass grafting can provide further benefit. The myocardialsparing effect of the harness, by decreasing wall tension, has beenshown experimentally to reduce myocardial energy consumption andtherefore reduce myocardial oxygen demand. If a bypass graft shouldbecome stenosed over time and cause the myocardium to become ischemic,the harness may attenuate any remodeling that might result. In additionto being an accompaniment to coronary artery bypass grafting,application of the cardiac harness might occur at the time of aortic ormitral valve repair or replacement surgeries.

[0096] Hinges 6 can be disposed in helical elements, also referred to inthis discussion as rings 80, rows, or strips 20, around thecircumference of the left ventricle or the heart. Strips 20 can containone or more connected hinges 6. Hinges 6 in a strip 20 are oriented tohave the same axis of elasticity as other hinges 6 in a strip 20. Strips20 can be joined or they can be independent of one another. As shown inFIGS. 8a-8 e, strips 20 of hinges 6 can be joined by interconnectingelements 16 in a variety of ways. For example, an interconnectingelement 16 can join the arm portion of one hinge 6 within a first strip20 to a central portion 8 of a hinge 6 in a second strip 20.

[0097] In FIG. 8b another configuration is illustrated. The centralportion of a hinge 6 within a first strip 20 is joined to the centralportion of another hinge 6 in a second strip 20, by an interconnectingelement 16. As illustrated in FIG. 8c, the interconnecting element 16can be angled to provide a spring-like mechanism between strips 20.

[0098]FIG. 8d shows another configuration of the interconnecting element16, providing firmer support between hinges 6 in different rows 20.

[0099] Joined strips 20 can be linked by longitudinally oriented hinges18 which act as interconnections between strips 20. These longitudinallyoriented hinges 18 provide elastic recoil in the longitudinal direction,while the strips 20 of hinges 6 provide the usual elasticity in thetransverse direction. This arrangement imparts a more isotropic elasticstructure than the previously described embodiments.

[0100] An advantageous feature of the preferred embodiment is thedecoupling of the action of the harness in the circumferential ortransverse dimension from the longitudinal direction. This decoupling isaccomplished by allowing a hinge 6 to stretch or bend circumferentially,or transversely, without pulling much longitudinally on the adjacenthinges. This principal is illustrated in FIGS. 9a-9 c. The relaxed, orend-systolic, configuration of the rows or strips 20 of hinges 6 isshown in FIG. 9a. There is considerable longitudinal overlap between thehinges 6 from one strip to another. In FIG. 9b, one can see that bypulling the strips apart in the longitudinal direction (along the Yaxis), there is a little or no foreshortening of the strips 20 of hinges6 in the transverse direction (i.e., along the X axis). This lack offoreshortening in the X axis is due to the fact that pulling apart thestrips 20 of hinges 6 in the Y direction produces very littlecompression of the hinges 6.

[0101]FIG. 9c illustrates a corollary property of the hinges 6, mostreadily seen when the cardiac harness 4 is applied to a live heart 2:The stretching of the strips 20 of hinges 6 in the transverse (X-axis)direction produces very little or no foreshortening in the longitudinal(Y-axis) direction. In the region of the cardiac base, which is close tothe outflow (aortic and pulmonic) valves, it is advantageous to have therows 20 of hinges 6 expanding and contracting in the circumferential ortransverse direction (i.e., along the X axis) while little or noforeshortening in the longitudinal direction (i.e., along the Y axis)occurs. This phenomenon is illustrated in FIG. 9c. Closer to the cardiacapex, it may be more advantageous to have the rows or strips 20 ofhinges 6 move apart in the longitudinal direction (i.e., along the Yaxis) while there is very little or no foreshortening in thecircumferential or transverse direction (i.e., along the X axis). Thisphenomenon is illustrated in FIG. 9b.

[0102] An additional way that the longitudinal expansion of the harnesscan be decoupled from the transverse expansion of the harness is throughthe use of elastically recoiling interconnecting elements 16, asillustrated in FIGS. 8a and 8 c. Additionally, having interconnectinghinges 18, as illustrated in FIG. 8e, is an additional way of decouplingthe longitudinal from transverse expansion and contraction of the hinges6 within the harness 4.

[0103] Alternatively, as illustrated in FIGS. 10 and 11, the rows orstrips 20 of hinges 6 can be interlocked (FIGS. 10a and 10 b) orinterwoven (FIGS. 11a and 11 b). To interlock strips 20 of hinges 6, thecentral portion 8 of a hinge 6 from a first row, or strip 20, is placedbetween the arms 10 of a hinge from a second row. This placement of a“hinge within a hinge” occurs for one or more hinges 6 in a first strip20, relative to the hinges in a second strip. To interweave strips 20 ofhinges 6, as illustrated in FIGS. 11a and 11 b, the strips 20 areconfigured such that one arm 10 of a first hinge 6 from a first strip 20lies under the central portion 8 of a second hinge from a second strip,while the other arm 10 of the first hinge 6 lies over the centralportion 8 of the second hinge from the second strip.

[0104] Another embodiment comprises a variable hinge network (notillustrated). In this network, hinges within a strip vary in height.Thus, a short hinge may be followed by a tall hinge, followed by a shorthinge, and so on within a strip. This variable hinge network providesthe capability to tailor the stiffness of the harness such that thestiffness varies with the degree of stretch. For example, at some firstthreshold of distension, the tall hinges deform, and at some higherthreshold of distension, the shorter hinges, which are stiffer, begin todeform. This arrangement can advantageously provide apressure-versus-diameter curve for the harness that exhibits twodistinct stiffness peaks at different diameters—with diametercorresponding to ventricular wall stretch or degree of distension.

[0105] An important difference between the decoupled hinge harnessconstruction of the preferred embodiment and a knitted fabric harness,or cardiac “sock,” is the hinge harness's ability to closely trackchanges in sphericity of the underlying heart, whether the heart ishealthy or diseased. This has been demonstrated experimentally by usingan inflated latex bladder, which simulates a heart in its expansion andcontraction. First, relative changes in sphericity of the bladder weremeasured. Note that sphericity is defined as diameter (D) divided bylength (L): ${sphericity} = \frac{diameter}{length}$

[0106] This relationship is illustrated in FIG. 12, which shows thediameter (D) of the heart in the transverse dimension and the length (L)of the heart in the longitudinal direction. The results of thisexperiment are illustrated in FIG. 13. When the bladder was inflatedalone (i.e., without the presence of a harness), it generated asphericity-versus-volume curve that is illustrated as the middle curvein FIG. 13. When a polyester knit “sock” was applied to the bladder,there was a great increase in sphericity as the volume of the bladderincreased, as illustrated by the top curve of FIG. 13. In contrast, whenthe elastic hinge harness 4 of the preferred embodiment was applied tothe bladder, the sphericity-versus-volume curve more closely matchedthat of the unencumbered bladder alone. The elastic hinge harnesssphericity curve is illustrated as the bottom curve in FIG. 13. Thus,the elastic hinge harness of the preferred embodiment closely trackschanges in sphericity over a range of volumes of the underlyingstructure, in this case a latex bladder. The nonforeshortening elastichinge harness 4 had little impact on the sphericity index as bladdervolume increased. In fact, the sphericity index values were slightlylower than for the bladder alone. In contrast, the presence of theknitted sock significantly increased the sphericity of the bladder asits volume was increased. This demonstrates the potential importance ofthe nonforeshortening elastic feature of the harness with respect to itsapplication to the human heart. The harness has the ability either (1)to “track” (i.e., minimally alter) changes in sphericity of one or bothventricles throughout systole and diastole; or (2) to progressivelydecrease the sphericity index of the heart, relative to an unencumberedheart (i.e., without the harness), as diastole proceeds, whether theheart is healthy or in congestive failure.

[0107] The hinges 6 can be made of a variety of materials, includingmetals, polymers, composites, ceramics, and biologic tissue. Specificmaterials include stainless steel, Elgiloy, titanium, tantalum, Nitinol,ePTFE, collagen, nylon, polyester, and urethane. Advantageously, thehinges are made from a metal, particularly Nitinol, because metals havea higher Young's modulus or stiffness, than polymers or tissue. Thisallows less mass and volume of material to be used to achieve the samemechanical reinforcing strength. Prosthetic materials that are directlyapplied to the epicardium, especially if there is some relative movementbetween the epicardium and the material, can induce fibrosis, which ismarked by collagen deposition leading to scarring. Consequently, animplant with less surface area in contact with the epicardium tends togenerate less fibrosis on the surface of the heart. Excessive fibrosiscan lead to a constrictive pericarditis and, ultimately, to elevatedvenous pressures with disastrous consequences.

[0108] Nitinol is especially suitable for the construction of theharness 4. It has the advantageous capability of being able to remainelastic over a great range of strain, up to 4%, which is greater thanother metals. It generates a relatively benign foreign body responsefrom tissue, and it is relatively magnetic-resonance-imaging-compatible,as it is not highly ferromagnetic. Nitinol is also corrosion- andfatigue-resistant. In addition, metal such as Nitinol are morecreep-resistant than polymeric or tissue based materials. In a passiveelastic harness application, hinge 6 would be formed in an austeniticstate at body temperature when no load is applied and the material is ina stress-free state. When the harness is placed on the heart, thecontact pressure between the harness and the heart may stress-inducemartensite within the otherwise austenitic structure.

[0109] The hinge elements can be made from wire, or they may be machinedfrom sheet or tubing material, or a combination of these. In order tomake such a structure out of Nitinol wire, the wire is wound andconstrained in the desired configuration. It is then annealed atapproximately 470° C. for approximately 20 minutes to set the shape.Alternatively, Nitinol tubing can be machined with a laser to create thedesired structure. Another alternative is the photochemical etching ofsheets of Nitinol. In both of these latter methods, a subsequentannealing can be performed.

[0110] In addition to varying the direction of elastic support, theextent of support or stiffness can be varied as well. Hinges ofdifferent shape or of different material dimensions can accomplish this.Because of the difference in compliance between the left and rightventricles, it can be desirable to have the left side of the harnessstiffer than the right side. This can be achieved in several ways. Aharness structure can be constructed with stiffer hinges against thesurface of the left ventricle than the right, as illustrated in FIG. 14.The hinges covering the left ventricle 22 are thicker, smaller, orotherwise stiffer than the hinges covering the right ventricle 24. Alsoshown in FIG. 14 are the individual strips 20 of binges, as well as theinterventricular septum 25, between left ventricle (LV) and rightventricle (RV).

[0111] In a preferred arrangement, a wire or plastic frame comprisingtwo struts (not illustrated) can be integrated with the harness 4. Theframe acts similarly to a clothespin, in that it exerts a clampingpressure along vectors 180 degrees apart, limiting the amount theventricle(s) are allowed to distend. The amount of pressure exerted bythe frame can be adjusted by making the frame larger or smaller, orthicker or thinner. The harness can also feature more than one frame.The harness's hinges 6 positioned between the wire frames, or betweenstruts of frames, can be of varying thickness or size to apply varyingstiffness and to allow for more or less ventricular distension.

[0112] In another embodiment, illustrated in FIG. 15, the cardiacharness may be selectively applied to only the left ventricle (or theright ventricle), depending on which side has failed. In thisillustration, the cardiac harness is applied to the left ventriclebecause the left ventricle fails far more often than the rightventricle. The harness may be anchored to the left ventricle in avariety of ways, including having anchoring struts that extend into theinterventricular septum 25, as shown in FIG. 15.

[0113] Advantageously, most or all of the surface of the left ventricleis covered by the harness 4. This ensures maximum reinforcement bothglobally, to attenuate global shape change and dilatation, and locally,to prevent ventricular wall thinning and stretch in an infarcted area.Note that this not to say that the actual surface area of the harness incontact with the epicardium needs to be large.

[0114]FIGS. 16a and 16 b illustrates a protection mechanism forminimizing compression of one or more coronary arteries 26. To minimizethe risk of ischemia, the compression of the harness on an epicardialcoronary artery 26 can be alleviated by placement of protecting strips28 on either side of the coronary artery 26. This mechanism lifts theharness 4 off of the coronary artery 26. A suitable material for theprotecting strip 26 can be expanded polytetrafluoroethylene ePTFE.

[0115] Another approach to minimizing compression of the coronary artery26 is illustrated in FIG. 17. A wire frame 30 that runs parallel to thecoronary artery 26 can be integrated into the harness 4. The hinges 6can be suspended from the wire frame 30 like curtains on a curtain rod.The hinges 6 extend from one arm of the wire frame 30 to the other overthe surface of the myocardium, between coronary arteries.

[0116] Advantageously, the compliance of the elastic harness 4 is in therange of compliance of native pericardium or latissimus dorsi musclewraps. Preferably, the compliance of the harness 4 increases graduallyas a function of stretch. Over the operational range of the harness,compliance should not fall so low that the harness 4 becomesconstrictive. Therefore, the pressure exerted on the heart 2 by theharness 4 preferably does not exceed 10 mm Hg. However, if only the leftventricle is reinforced by the harness 4, then greater pressures arepossible without causing constrictive conditions.

[0117] Various designs incorporating decoupled hinges 6 are possible.The hinges 6 can wrap continuously around both ventricles or just aroundthe left ventricle or right ventricle. The harness 4 can have a seam forsize adjustment, or it can be of a one-size-fits-all design. A Nitinolharness can be provided presized to fit the dimensions of a patient'sheart. Alternatively, the harness components can be provided in a kitthat a surgeon can custom-assemble in the operating room, based onsizing information gained before or at the time of surgery. A kit canconsist of modular components that can be assembled quickly. The use ofhinge strips 20 that are ring-shaped and of varying diameters andstiffness is one possibility. The surgeon can interlock hinges 6 betweenadjacent hinge strips 20 in order to couple the strips 20, asillustrated in FIG. 10b. Precise sizing can be facilitated by using abelt buckle or adhesive fastener (e.g., a hook-and-loop fastener, suchas Velcro™) type of design, as illustrated in FIGS. 18a and 18 b. FIGS.18a and 18 b illustrate the harness 4 wrapped around the heart 2, with aleading flap 32 that integrates an adhesive strip, such as Velcro™, forsecuring the harness 4 onto the heart 2. Such a design is not readilyachievable using the knitted sock of previous designs.

[0118] Delivery of the harness 4 can be accomplished throughconventional cardiothoracic surgical techniques through a mediansternotomy. Alternatively, the harness 4 may be delivered throughminimally invasive surgical access to the thoracic cavity, asillustrated in FIG. 19. A delivery device 36 may be inserted into thethoracic cavity 34 between the patient's ribs to gain direct access tothe heart 2. Preferably, such a minimally invasive procedure isaccomplished on a beating heart, without the use of cardiopulmonarybypass. Access to the heart can be created with conventional surgicalapproaches. The pericardium may be opened completely, or a smallincision can be made in the pericardium (pericardiotomy) to allow thedelivery system 36 access to the heart 2. The delivery system 36 of thedisclosed embodiments comprises an integrated unit of severalcomponents, as illustrated in FIGS. 20a and 20 b. Preferably, there is areleasable suction device, such as a suction cup 38, at the distal tipof the delivery device 36. This negative pressure suction cup 38 is usedto hold the apex of the heart 2. Negative pressure can be applied to thecup 38 using a syringe or other vacuum device. A negative pressure lockcan be achieved through a one-way valve, stopcock, or a tubing clamp.The suction cup 38, advantageously formed of a biocompatible material,is preferably stiff to prevent any negative pressure loss through heartmanipulation. this provides traction by which the harness 4 can bepushed forward onto the heart 2. In addition, the suction cup 38 can beused to lift the heart 2 to facilitate advancement of the harness 4 orallow visualization and surgical manipulation of the posterior side ofthe heart 2. After secure purchase of the apex of the heart 2 isachieved, the harness 4, which is collapsed within the body 46 of thedelivery device 36, is advanced distally toward the heart 2 by actuatingfingers 40. The harness 4 can be inverted (i.e., turned inside-out)ahead of time, to allow it to unroll, or evert as it advances over thesurface of the heart 2. In this discussion, the term “evert” meansturning right-side-in, i.e., reversing an inverting process. After theharness 4 is advanced into place, the suction is released and thedelivery system 36 is released from the harness 4 and heart 2.

[0119] FIGS. 21-25 illustrate the application of the cardiac harness 4to the heart 2 in various stages. FIG. 21 shows the delivery device,which may be a catheter in one embodiment, comprising a body 46 and ahandle 44. The catheter body 46 is advanced through the skin 48 of thepatient. The suction 38 moves in proximity to the apex 42 of the heart2. The harness 4 is inverted (i.e., turned inside out) and is collapsedwithin the body 46 of the delivery device.

[0120]FIG. 22 illustrates engagement of the apex 42 of the heart 2 bythe suction cup 38. Suction may be applied to the apex 42 of the heart 2by moving the handle 44 in one or more directions, or by using a syringeor other suction device (not illustrated).

[0121]FIG. 23 shows advancement of the harness 4 by the actuatingfingers 40 within the body 46 of the delivery device. The harness 4 maybe advanced over the heart 2 by moving the handle 44 toward the heart 2relative to the body 46 of the delivery device.

[0122]FIG. 24 shows further advancement and unrolling, or everting, ofthe harness 4 as the actuating fingers 40 move distally and outwardlyrelative to the delivery device body 46. The suction cup 38 remainsengaged on the heart 2.

[0123]FIG. 25 illustrates completion of the placement of the harness 4on the heart 2. After the harness 4 is in position on the heart 2, thehandle 44 may be withdrawn from the body 46 of the delivery device,pulling the actuating finger 40 back within the body 46 of the deliverydevice. The suction cup 38 is also released from the heart 2 and harness4, and the delivery device is withdrawn from the patient through theskin 48.

[0124]FIGS. 26a-26 d illustrate another embodiment of the deliverydevice, in which the actuating fingers 40 of the device form a loop or“flower petal” configuration. The actuating fingers 40 are withdrawnwithin the body 46 of the delivery device in FIG. 26a. FIGS. 26b and 26c show a progressive advancement of the actuating fingers 40 distallyfrom the body 46 of the delivery device. As the fingers 40 advance, theyexpand outwardly into a larger loop or flower petal configuration. FIG.26d is an en face view of the delivery device body 46 and theflower-petal-shaped actuating fingers 40.

[0125] The harness 4 can be secured in place on the heart 2, usingsutures or staples to prevent it from migrating. Alternatively, theharness 4 can self-anchor to the epicardium to prevent it frommigrating. This self-anchoring can be accomplished by incorporatinginward-facing barbs or anchors 50 in the harness structure 4, asillustrated in FIGS. 27a and 27 b. The anchors 50 preferably extend fromthe hinges 6 into the wall of the heart 2.

[0126]FIG. 28 shows an alternative embodiment of the delivery device.The body 46 of the delivery device is curved to facilitate placementand/or manipulation of the device by the surgeon. Also illustrated is asyringe 52 for injecting fluids or for generating suction on the distalsuction cup 38 to secure the suction cup 38 to the apex 42 of the heart2. Also illustrated is the harness 4 that is partially withdrawn withinthe body 46 of the delivery device.

[0127]FIG. 29 shows an alternative embodiment of the delivery device.The body 46 of the delivery device is straight in this embodiment.

[0128]FIG. 30 illustrates advancement of the harness 4 and actuatingfingers 40 onto the heart 2.

[0129]FIG. 31 shows completed placement of the harness 4 onto the heart2 by the delivery device. Note that the actuating fingers 40 form aloop, and, in some embodiments, the actuating fingers 40 are made offlexible material to form flexible straps or bands.

[0130] The harness 4 not only has the capability of acting as a passiverestraint around the heart, but may also be actively powered to providecontractile assistance during systole. This may be done by theapplication of electrical or mechanical power to the harness 4.

[0131] If electrical current or heat is applied to the harness 4 in thestressed state, the resistive force generated by the bending deformationincreases. In essence, the harness 4 generates a contractile force whencurrent is applied to the harness 4. Hence, it is possible to activelypower an otherwise passive elastic harness 4 in order to achievesystolic pumping assistance. This effect is additive in the myocardialsparing benefit that the harness 4 provides.

[0132] During systole and perhaps at end-diastole, current can beapplied to the harness 4 to make it contract and thus assist in leftventricular contraction. Such a mechanism is illustrated in FIG. 32. Theharness 4 surrounds the heart 2. An electrical wire 60 extends from aninternal power supply 54 to the harness 4.

[0133] In this context, the internal power supply 54 is a device thatsupplies electrical energy to the harness 4. It may also comprise abattery and, in some embodiments, a radiofrequency transducer forreceiving and/or transmitting radiofrequency signals to and from anexternal radiofrequency (“RF”) transducer 56 which may send and/orreceive RF signals from the internal power supply 54. Thus, the externalRF transducer 56 may recharge a battery within the internal power supply54. Also, the external RF transducer 56 may be used to send programinformation from the external RF transducer 56 to the internal powersupply 54, or vice versa, regarding electromechanical sensing and/orpacing information, cardiac rhythm, degree of ventricular or harnesscontractility, heart-rate information, or the like. Alternatively, theexternal RF transducer 56 may supply electrical power through inductivefield coupling between the external RF transducer 56 and the internalpower supply 54.

[0134] In some embodiments, an external power supply 58 can be used,which may be a battery pack in various preferred arrangements. Theexternal power supply 58 may supply current to the external RFtransducer 56, which may in turn supply electrical energy to theinternal power supply 54 through inductive field coupling. Thetechnology for this inductive field coupling, including electronicprogramming and power transmission through RF inductive coupling, hasbeen developed and is employed in, for example, cardiac pacemakers,automatic internal cardiac defibrillators, deep brain stimulators, andleft ventricular assist devices.

[0135] The power requirement of the device of the disclosed embodimentsis significantly lower than that of conventional left ventricular assistdevice because the native heart in the present application continues todo some work. The powered harness 4 merely augments native cardiaccontractions.

[0136] Rather than a Nitinol harness 4 providing active systolicassistance, variable current can be applied to the Nitinol to simplyvary the harness's 4 passive stiffness. As such, power is not used toactively “squeeze” the heart 2 during systole. The harness 4 is insteada passive elastic harness with adjustable compliance. A physician canadjust the power to a harness 4 to vary the amount of resistive pressureit exerts on the left ventricle during both systole and diastole. Thepassive stiffness of the harness 4 can be set to change throughout thecardiac cycle, or it can be adjusted to maintain constant levels. Forexample, when the cardiac harness 4 is placed on the heart 2, thephysician can set the harness 4 to a certain degree of stiffness.Depending on how the patient responds, the physician can then increaseor decrease stiffness by varying the electrical stimulating parametersto the harness 4. Adjustment and stimulation of the harness 4 can beaccomplished through an implantable pacemaker-like box, the internalpower supply 54, that is electrically connected to the harness 4 throughat least one wire 60. This is one embodiment of the configurationillustrated in FIG. 32.

[0137] The harness 4 may be integrated with an implantable pacemaker ora internal cardiac defibrillator, according to the needs of the patient.

[0138] Mechanical power can be applied to the harness 4 through slidingcables 70 as illustrated in FIGS. 33 and 34. A cable 70 can extend overthe surface of the harness 4 between two points. The cable 70 isactually an inner sliding element that resides partially within an outerhousing 68. Mechanical actuation of the cable 70 by, for example, anactuation box 62 causes the two components, illustrated in FIGS. 33 and34 as struts 72 within the harness 4, to slide or otherwise moverelative to each other. If the end 74 of the housing 68 is attached toone strut 72, and the distal end of the cable 70 is attached to anotherstrut 72, then actuation of the cable causes the two struts to movecloser and/or farther apart relative to one another, causing the heartto contract and/or expand. If timed with systole, this mechanismprovides contractile assistance.

[0139] Also illustrated in FIGS. 33 and 34 are the actuation box 62,which converts electrical energy to mechanical energy to move the cable70 within the housing 68; a power lead line 64, extending from theinternal power supply 54 to the actuation box 62; and an electricalsensing lead 66, which can sense cardiac contractions or cardiacelectrical activity, such as an electrocardiographic signal. Thissensing is similar to the way in which pacemakers sense cardiacelectrical activity, receiving information concerning the rate andrhythm of the heartbeat. Also illustrated in FIGS. 33 and 34 are theexternal RF transducer 56 and the external power supply 58, aspreviously described.

[0140]FIG. 33 illustrates the struts 72 as unattached to one another,while FIG. 34 shows the struts 72 attached at a point 76 near the apexof the heart 2. These two different embodiments can confer differentmechanical and hemodynamic advantages upon actuation of the cable 70 andconsequent contraction and expansion of the heart 2.

[0141]FIG. 35a-36 b illustrate a method of manufacturing the strips, orrows, of hinges 6. A sheet (or more than one sheet) of Nitinol or othersuitable material is cut to form a single, continuous ring 80 of hinges6. This ring 80 is initially flat after it has been cut from the sheetof material, as shown in FIG. 35a (top view) and 35 b (side view). Thering 80 is preferably parallel to the surface (e.g., a table or board)on which the ring 80 is formed. The ring is then manipulated to create aband-like configuration, which can be cylindrical or beveled, asillustrated in FIG. 36a (top view) and 36 b (side view).

[0142] Compared to conventional left ventricular assist devices, theharness 4 of the disclosed embodiments has many advantages. It can beminimally invasively delivered, and it can be permanently implantedwithout need for subsequent removal. This allows it to provideincremental therapy as needed. If necessary, it can be powered toprovide contractile assistance. If this is not necessary, the power canbe shut off to allow it to act as a passive elastic reinforcement forthe failing heart.

[0143] In addition, such a system can provide circulatory assistancewith a fraction of the power demands of a left ventricular assistdevice. Left ventricular assist devices are estimated to require nearlyten watts of power. The heart itself operates at only approximately onewatt of power. Because a powered harness works with the existing heart,it should not need nearly the amount of power of a left ventricularassist device. In addition, because the harness 4 does not come indirect contact with blood, there is no need to anticoagulate the patientwith, for example, warfarin (Coumadin) or heparin. There is also noindependent reason to treat the patient with antiplatelet drugs. Aharness system involves less machinery than a left ventricular assistdevice. This and other attributes impose less detriment to a patient'squality of life. Last, such a system is relatively simple and thereforeless costly than a left ventricular assist device.

[0144] Power to actuate the cable 70 can come from an internal orexternal source. An internal source can alternatively be skeletalmuscle, such as in situ latissimus dorsi muscle or a mechanical motor.If power is needed, it can be delivered transcutaneously as describedabove, using existing technology developed by, for example,left-ventricular-assist device companies.

[0145] Although the present invention has been described in terms ofcertain preferred embodiments, other embodiments that are apparent tothose of ordinary skill in the art are also within the scope of theinvention. Accordingly, the scope of the invention is intended to bedefined only by reference to the appended claims.

What is claimed is:
 1. An cardiac harness for treating or preventingcongestive heart failure, comprising: a plurality of interconnectedelastic bending hinges, each bending hinge comprising a central portionconnected on opposite sides to respective arm portions, said armportions interacting with said central portion in response to deflectionof said arm portions to create a bending moment in said hinge to storepotential energy.
 2. The cardiac harness of claim 1, wherein saidbending hinges are substantially U-shaped.
 3. The cardiac harness ofclaim 1, wherein said bending hinges are substantially V-shaped.
 4. Thecardiac harness of claim 1, wherein said bending hinges aresubstantially square-wave-shaped.
 5. The cardiac harness of claim 1,wherein said bending hinges are substantially teardrop-shaped.
 6. Thecardiac harness of claim 1, wherein said bending hinges aresubstantially keyhole-shaped.
 7. The cardiac harness of claim 1, whereinsaid at least one of said bending hinges from a first row is connectedto another of said bending hinges from a second row.
 8. The cardiacharness of claim 1, wherein said bending hinges are formed from at leastone strand of Nitinol.
 9. The cardiac harness of claim 1, wherein saidat least one strand comprises a wire.
 10. The cardiac harness of claim1, wherein said at least one strand comprises a ribbon.
 11. The cardiacharness of claim 1, further comprising a power source that suppliesenergy to said harness, causing said harness to contract.
 12. Thecardiac harness of claim 11, wherein said power source deliverselectrical energy to at least one of said bending hinges, causing atleast one of said bending hinges to produce said bending moment.
 13. Thecardiac harness of claim 11, wherein said power source deliversmechanical energy to said cardiac harness through a cable.
 14. Thecardiac harness of claim 11, wherein said power source is programmablevia transcutaneous radiofrequency signals.
 15. The cardiac harness ofclaim 11, wherein said power source is rechargeable via transcutaneouselectromagnetic coupling.
 16. The cardiac harness of claim 11, whereinsaid power source is rechargeable via transcutaneous inductive fieldcoupling.
 17. An apparatus for treating or preventing congestive heartfailure, comprising: a cardiac harness having a plurality of springelements, said harness adapted to be placed around at least a cardiacbase; wherein said spring elements interact such that said harnessexpands and contracts in a substantially transverse dimension of saidharness in the region of the cardiac base in response to the mechanicalcardiac cycle, without substantial expansion or contraction in thelongitudinal dimension of said harness in the region of the cardiacbase.
 18. The apparatus of claim 17, wherein said spring elementscomprise of Nitinol.
 19. An apparatus for treating or preventingcongestive heart failure, comprising: a cardiac harness having aplurality of spring elements, said harness adapted to be placed aroundat least a cardiac apex; wherein said spring elements interact such thatsaid harness expands and contracts in a substantially longitudinaldimension of said harness in the region of the cardiac apex in responseto the mechanical cardiac cycle, without substantial expansion orcontraction in the transverse dimension of said harness in the region ofthe cardiac apex.
 20. The apparatus of claim 19, wherein said springelements are comprise Nitinol.
 21. An apparatus for treating orpreventing congestive heart failure, comprising: at least one elongatestrip sized to fit around at least a base of a ventricle of a heart,such that said strip extends substantially transverse to thelongitudinal axis of the heart, said strip comprising at least onespring element, said at least one spring element configured to causesaid strip to provide force against said at least a base of a ventriclein a substantially transverse direction without substantial force in alongitudinal direction.
 22. The apparatus of claim 21, wherein saidstrip surrounds the heart.
 23. The apparatus of claim 21, wherein saidstrip surrounds the left ventricle.
 24. The apparatus of claim 21,wherein said strip surrounds the right ventricle.
 25. The apparatus ofclaim 21, wherein said strip comprises at least one undulating strand.26. The apparatus of claim 21, wherein said at least one spring elementcomprises a central portion and two arm portions.
 27. The apparatus ofclaim 21, wherein said at least one spring element comprises Nitinol.28. An apparatus for treating or preventing congestive heart failure ina heart having a ventricle that changes sphericity in response todiastolic filling, said apparatus comprising: a harness comprising aplurality of interconnected spring elements, said harness limitingdiastolic distention of said ventricle to a degree of expansion withoutsubstantially altering naturally occurring changes in said sphericitythrough said degree of expansion caused by diastolic filling of saidheart.
 29. The apparatus of claim 28, wherein at least one of saidspring elements comprises Nitinol.
 30. An apparatus for treating orpreventing congestive heart failure in a heart having a ventricle thatchanges sphericity in response to diastolic filling, said apparatuscomprising: a harness comprising a plurality of interconnected springelements, said harness limiting diastolic distention of said ventricleto a degree of expansion while substantially decreasing the magnitude ofa naturally occurring increase in said sphericity through said degree ofexpansion caused by diastolic filling.
 31. The apparatus of claim 30,wherein at least one of said spring elements comprises Nitinol.
 32. Aharness for treating or preventing congestive heart failure, comprising:a series of interconnected spring elements, each spring elementcomprising: a central portion; and a pair of arm portions extendingalong respective paths that originate at respective sides of the centralportion and converge toward each other along at least a portion of saidpaths as said paths extend away from said central portion.
 33. Theharness of claim 32, wherein at least one of said spring elementscomprises Nitinol.
 34. A cardiac harness, comprising: first and secondstrands of material each having a plurality of hinges, each of saidhinges formed by a pair of arm portions extending from a centralportion, each hinge within said plurality of hinges of the first strandhaving both arm portions disposed within a hinge of the second strand,between the arm portions of said hinge of the second strand.
 35. Thecardiac harness of claim 34, wherein at least one of said hingescomprise Nitinol.
 36. The cardiac harness of claim 34, wherein at leastone of said strands comprises a band.
 37. A method of assembling acardiac harness, comprising: providing a plurality of rings, each ofsaid rings having a series of periodic undulations, each of said ringsbeing unattached to other of said rings; and interconnecting the ringsby interleaving said undulations without interrupting continuity of therings.
 38. The method of claim 37, wherein at least one of said ringscomprises Nitinol.
 39. A cardiac harness, comprising: a plurality ofinterconnected spring elements comprising Nitinol.
 40. An apparatus fortreating or preventing congestive heart failure, comprising: a cardiacharness comprising interconnected strands of material; at least one padhaving a marginal edge that is oriented for placement in proximity to atleast one coronary artery, so as to reduce compression of said artery bysaid harness.
 41. The apparatus of claim 40, wherein said materialcomprises Nitinol.
 42. An apparatus for treating or preventingcongestive heart failure, comprising: a cardiac harness comprisinginterconnected strands of material which traverse an exterior surface ofa ventricle of the heart, without traversing a substantial portion ofthe length of at least one coronary artery selected from the groupconsisting of the left anterior descending artery, the right coronaryartery, the left circumflex artery, the posterior descending artery, andthe obtuse marginal artery.
 43. The apparatus of claim 42, wherein saidmaterial comprises Nitinol.
 44. The apparatus of claim 42, wherein theharness comprises a support member which supports a portion of saidstrands, said member having side portions disposed on opposite sides ofsaid at least one coronary artery.
 45. An apparatus for delivering acardiac harness having side portions and an apex portion, comprising: acatheter body having a distal end portion, configured to retain saidharness in a substantially inverted condition with an interior side ofthe harness facing outward away from a ventricle and an exterior sidefacing inward toward said ventricle; an activation member which ismovable relative to said catheter body, the apex portion of said harnessreleasably connected to the catheter body, said activation memberdriving said side portions of said harness distally and outwardlyrelative to said apex portion such that said harness expandscircumferentially, whereby said harness everts to at least partiallysurround the ventricle, with said interior side of the harness facinginward toward said ventricle and said exterior side facing away fromsaid ventricle.
 46. The apparatus of claim 45, wherein said distal endportion comprises a suction cup.
 47. A method of delivering a cardiacharness, comprising: providing a catheter having an inverted harnessmounted on a distal end portion of said catheter; inserting saidcatheter into a thorax such that an apex portion of said invertedharness is proximate to the apex of a ventricle; everting side portionsof said harness while said apex portion of said harness remainspositioned proximate to an apex of said ventricle.
 48. The method ofclaim 47, wherein said cardiac harness comprises Nitinol.
 49. A methodof manufacturing a cardiac harness, comprising: forming an elongatemember having undulations from a sheet of material.
 50. The method ofclaim 49, wherein said material comprises Nitinol.
 51. The method ofclaim 49, wherein said forming said elongate member comprises formingsaid undulations in a plane substantially parallel to said sheet ofmaterial.
 52. The method of claim 51, wherein said forming comprisescutting said elongate member on a flat surface.
 53. The method of claim51, further comprising annealing said material with the undulationsoriented at a substantial angle relative to said plane.